Aligned molecules promise faster telecommunications

Date: 4 February 2015

Introduction: Antwerp researchers have succeeded in aligning asymmetric molecules inside nanotubes for the first time. While this scoop is obviously of great fundamental scientific value, in the future it may also lead to applications in optical telecommunications. The publication of the results in Nature Nanotechnology has already proven the importance of the finding.

A green laser pointer is a common example of a nonlinear optical device, which converts invisible infrared laser beams to bright green ones. Devices like these work using inorganic crystals, which are also widely used to modulate light for telecommunication through optical fibres. But the crystals have a relatively slow response time. “That response time limits the rate at which you can transmit data”, explains Jochen Campo (University of Antwerp).

With his colleagues Professor Wim Wenseleers and Sofie Cambré from the Department of Physics, Campo has been experimenting with faster organic molecules for some years. In order for such molecules to be useful, they need to be asymmetric and aligned in the same direction. Campo: “This alignment was a major problem, because opposite charges attract each other. Think of two bar magnets: when you throw them towards each other, they stick together side-by-side but in opposite directions, so that together they are useless. If you inserted them into a thin tube one after the other, however, they would combine to form one strong magnet.”

The molecules in Figure A cancel each other out; the aligned molecules in B enhance each other’s properties.

The Antwerp team has now become the first to succeed in aligning organic molecules by inserting them into carbon nanotubes. Cambré: “These tubes consist of a single layer of carbon atoms, rolled up to form cylinders with a diameter of only one nanometre, which fit the molecules perfectly. They are the strongest fibres known to man - incredibly strong but also light as a feather. Because of this, they also protect the rather delicate organic molecules.”

Aligned molecules cooperate to yield a giant response. “Our concept is generally applicable,” explains Wim Wenseleers, “to various molecules and a wide range of properties. This finding is of great value from a purely scientific point of view, but it may also lead to a wide range of applications. For instance, it could be used to make materials for faster optical data communication.”